P: Camera Raw 9.3: Broken "Default Develop Settings"

Massive issue after updating to Lightroom 6.3.
The “Default Develop Settings” isn’t working, the settings are reset every time you start Lightroom.
I’ve got hundreds of default settings for different ISOs saved for a number of cameras, all don’t work.
The folder with the Default Develop Settings still contains all my defaults:
C:\Users\\AppData\Roaming\Adobe\CameraRaw\Defaults.
But they don't load anymore with Lightroom 6.3, so when I hit "reset" on a photo it resets the photo to lightroom default values instead of what I set in the "default develop settings".

When I try to set a new “Develop Setting”, let’s say, default develop setting for clarity on ISO100 photos is +10, it works for the duration of my lightroom session, BUT as soon as I close lightroom and restart it, the default develop setting doesn’t work, i.e. when I click "reset" on a photo, it resets the clarity back to 0 which is the lightroom default and not +10 which is my default for the ISO100 photo (this is of course a simplification of the problem).

Does anybody else have this issue? This is a very big deal for me, these default develops settings save me huge amounts of time normally...